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An action of a group $G$ on a compact space $X$ is called weakly almost periodic if the orbit of every continuous function on $X$ is weakly relatively compact in $C(X)$. We observe that for a topological group $G$ the following are…

General Topology · Mathematics 2016-09-07 Michael G. Megrelishvili , Vladimir G. Pestov , Vladimir V. Uspenskij

Given a smooth partial action $\alpha$ of a Lie groupoid $G$ on a smooth manifold $M,$ we provide necessary and sufficient conditions for $\alpha$ to be globalizable with smooth globalization. As an application, we provide results on the…

Differential Geometry · Mathematics 2024-12-31 Víctor Marín , Héctor Pinedo , J. L. V. Rodríguez

We prove that locally countably-compact Hausdorff topological groups $\mathbb{G}$ act continuously on their iterated joins $E_n\mathbb{G}:=\mathbb{G}^{*(n+1)}$ (the total spaces of the Milnor-model $n$-universal $\mathbb{G}$-bundles) as…

General Topology · Mathematics 2026-04-07 Alexandru Chirvasitu

A group $G$ is said to be a $C$-group if every subgroup $H$ has a permutable complement, i.e. if there exists a subgroup $K$ of $G$ such that $G=HK$ and $H \cap K=1$. In this paper, we study the profinite counterpart of this concept. We say…

Group Theory · Mathematics 2025-07-29 Gustavo A. Fernández-Alcober , Giulia Sabatino

We investigate some properties of the clopen type semigroup of an action of a countable group on a compact, $0$-dimensional, Hausdorff space X. We discuss some characterizations of dynamical comparison (most of which were already known in…

Dynamical Systems · Mathematics 2024-10-04 Julien Melleray

L\'evai and Pyber proposed the following as a conjecture: Let $G$ be a profinite group such that the set of solutions of the equation $x^n=1$ has positive Haar measure. Then $G$ has an open subgroup $H$ and an element $t$ such that all…

Group Theory · Mathematics 2020-01-22 Meisam Soleimani Malekan , Alireza Abdollahi , Mahdi Ebrahimi

The article deals with profinite groups in which the centralizers are pronilpotent (CN-groups). It is shown that such groups are virtually pronilpotent. More precisely, let G be a profinite CN-group, and let F be the maximal normal…

Group Theory · Mathematics 2018-09-13 Pavel Shumyatsky

We prove effective equidistribution, with polynomial rate, for large closed orbits of semisimple groups on homogeneous spaces, under certain technical restrictions (notably, the acting group should have finite centralizer in the ambient…

Dynamical Systems · Mathematics 2007-08-31 M. Einsiedler , G. Margulis , A. Venkatesh

We study profinite completion of spaces in the model category of profinite spaces and construct a rigidification of the completion functors of Artin-Mazur and Sullivan which extends also to non-connected spaces. Another new aspect is an…

Algebraic Topology · Mathematics 2011-11-21 Gereon Quick

For a complex variety $\hat X$ with an action of a reductive group $\hat G$ and a geometric quotient $\pi: \hat X \to X$ by a closed normal subgroup $H \subset \hat G$, we show that open sets of $X$ admitting good quotients by $G=\hat G /…

Algebraic Geometry · Mathematics 2016-11-10 Johannes Schmitt

We introduce and study the notion of continuous orbit equivalence of actions of countable discrete groups on Cartan pairs in (twisted) groupoid context. We characterize orbit equivalence of actions in terms of the corresponding…

Operator Algebras · Mathematics 2023-12-05 Massoud Amini , Mahdi Moosazadeh

In this paper we characterise the action of the absolute Galois group on the geometric finite cyclic groups without \'etale factorization of stack inertia of the profinite geometric fundamental group of moduli spaces of marked curves. As a…

Algebraic Geometry · Mathematics 2014-03-12 Benjamin Collas , Sylvain Maugeais

Let $G= N\rtimes H$ be a locally compact group which is a semi-direct product of a closed normal subgroup $N$ and a closed subgroup $H.$ The Bohr compactification ${\rm Bohr}(G)$ and the profinite completion ${\rm Prof}(G)$ of $G$ are,…

Group Theory · Mathematics 2023-05-09 Bachir Bekka

The aim of this short note is to investigate the geometry of weakly complete subdomains of Grauert type surfaces, i.e. open connected sets D, sitting inside a Grauert type surface X, which admit a smooth plurisubharmonic exhaustion…

Complex Variables · Mathematics 2018-10-15 Samuele Mongodi

We describe a cocompact model for the classifying space for proper actions of the mapping class group of a surface with punctures and boundary components. Our construction relies on a known model for the case of a closed surface and uses an…

Algebraic Topology · Mathematics 2009-05-07 Guido Mislin

When a discrete group admits a convex-cocompact action on a non-compact rank-one symmetric space, there is a natural lower bound for the Hausdorff dimension of the limit set, given by the Ahlfors regular conformal dimension of the boundary…

Metric Geometry · Mathematics 2018-06-13 Guy C. David , Kyle Kinneberg

We classify representations of compact connected Lie groups whose induced action on the unit sphere has an orbit space isometric to a Riemannian orbifold.

Differential Geometry · Mathematics 2017-03-14 Claudio Gorodski , Alexander Lytchak

The structure of finite and locally finite groups in which every element has prime power order (CP-groups) is well known. In this paper we note that the combination of our earlier results with the available information on the structure of…

Group Theory · Mathematics 2020-01-07 Pavel Shumyatsky

A closed subgroup $H$ of a locally compact group $G$ is confined if the closure of the conjugacy class of $H$ in the Chabauty space of $G$ does not contain the trivial subgroup. We establish a dynamical criterion on the action of a totally…

Group Theory · Mathematics 2022-12-09 Pierre-Emmanuel Caprace , Adrien Le Boudec , Nicolás Matte Bon

In this note we extend to metrizable profinite groups the classical theorems of Titchmarsh on the Fourier transform of H\"older-Lipschitz functions. This generalizes the results of Younis on compact zero-dimensional abelian groups to the…

Functional Analysis · Mathematics 2023-04-03 J. P. Velasquez-Rodriguez